With rapid development of video technologies, the application fields of the commercially available microphones become more expansive. For example, an electronic device such as a camcorder, a web camera or a headphone is usually equipped with a microphone for receiving sound.
For maintaining the product quality of the microphone, a quality control process is usually employed to inspect the quality of the microphone before the microphone is sold into the market. For example, an inspecting instrument is used to inspect the microphone to obtain the tested data and the tested waveform. Then, the tested data and the tested waveform are compared with the standard data and the standard waveform that are previously stored in the inspecting instrument.
However, since the microphone factory is an open place and the microphone is a sound-receiving device, the background noise resulting from the machinery operation or the noisy voice in the factory is inevitably received by the microphone. If the tested data and the tested waveform of the microphone are obtained in the factory, the tested data and the tested waveform may contain the tested data and the tested waveform of the background noise. In other words, it is not reasonable to compare the tested data and the tested waveform with the standard data and the standard waveform because the tested data and the tested waveform do not simply reflect the quality of the microphone itself but contain the background noise or other noise signals.
Furthermore, since the standard data and the standard waveform that are previously stored in the inspecting instrument, it is impossible to realize the extent of the influence of the current background noise on the inspected result of the microphone. In other words, it is not reasonable to compare the tested waveform with the standard waveform because the tested waveform does not accurately reflect the sound-receiving performance of the microphone. Under this circumstance, it is impossible to discriminate the difference between the qualified product and the unqualified product.
For solving the above drawbacks, the manufacturer of the microphone has to additionally build an anechoic chamber. The anechoic chamber is an independent soundproof testing area that is insulated from exterior sources of noise. The microphone to be inspected is disposed within the anechoic chamber to receive sound. By comparing the tested waveform of the microphone with the standard waveform, the unqualified microphone can be detected. However, since the transportation of the microphone from the factory to the anechoic chamber is labor-intensive and time-consuming, the way of inspecting the microphone in the anechoic chamber is not satisfied. Moreover, the cost of building the anechoic chamber is very high, and thus the cost associated with the microphone inspection is increased.
Therefore, there is a need of providing a microphone inspection method for accurately detecting the unqualified microphone even in the presence of background noise (e.g. in a factory) in order to increase the inspecting efficiency.